The isothermal internal friction of a Ag-42.3% Cd alloy has been measured by means of a low frequency inverted torsion pendulum apparatus between room temperature and 250℃. The relation between Q-1 and temperature with various heating and cooling rate were determined. Experimental results show that as the bainitic transformation occurs, the Q-1 of Ag-Cd alloy increases rapidly. It may be postulated that there are regions of instability of the parent lattice in the course of nucleation process for the bainitic transformation. The increment of Q-1s is a function of the product of internal friction of the fraction of the lattice localized soft region per volume and the nuclea-tion rate J* of the bainite.